需要帮助了解用法：功能

Question

我目前正在阅读Apple提供的Swift Developer书。我在“个性测验”项目中，对为什么按原样编写代码感到困惑。

问题出在updateSingleStack(using: currentAnswers)上。如果您看下面的代码，我会有些困惑using: currentAnswers的含义。

import UIKit

class QuestionViewController: UIViewController
{
    @IBOutlet weak var questionLabel: UILabel!

    @IBOutlet weak var singleStackView: UIStackView!
    @IBOutlet weak var singleButton1: UIButton!
    @IBOutlet weak var singleButton2: UIButton!
    @IBOutlet weak var singleButton3: UIButton!
    @IBOutlet weak var singleButton4: UIButton!

    @IBOutlet weak var multipleStackView: UIStackView!
    @IBOutlet weak var multiLabel1: UILabel!
    @IBOutlet weak var multiLabel2: UILabel!
    @IBOutlet weak var multiLabel3: UILabel!
    @IBOutlet weak var multiLabel4: UILabel!

    @IBOutlet weak var rangedStackView: UIStackView!
    @IBOutlet weak var rangedLabel1: UILabel!
    @IBOutlet weak var rangedLabel2: UILabel!

    @IBOutlet weak var questionProgressView: UIProgressView!

    var questions: [Question] =
    [
        Question(text: "Which food do you like the most?",
                 type: .single,
                 answers:
                 [
                     Answer(text: "Steak", type: .dog),
                     Answer(text: "Fish", type: .cat),
                     Answer(text: "Carrots", type: .rabbit),
                     Answer(text: "Corn", type: .turtle)
                 ]),

        Question(text: "Which activities do you enjoy?",
                 type: .multiple,
                 answers:
                 [
                     Answer(text: "Swimming", type: .turtle),
                     Answer(text: "Sleeping", type: .cat),
                     Answer(text: "Cuddling", type: .rabbit),
                     Answer(text: "Eating", type: .dog)
                 ]),

        Question(text: "How much do you enjoy car rides?",
                 type: .ranged,
                 answers:
                 [
                     Answer(text: "I dislike them", type: .cat),
                     Answer(text: "I get a little nervous", type: .rabbit),
                     Answer(text: "I barely notice them", type: .turtle),
                     Answer(text: "I love them", type: .dog)
                 ])
    ]

    var questionIndex = 0

    override func viewDidLoad()
    {
        super.viewDidLoad()
        updateUI()
    }

    func updateUI()
    {
        singleStackView.isHidden = true
        multipleStackView.isHidden = true
        rangedStackView.isHidden = true

        let currentQuestion = questions[questionIndex]
        let currentAnswers = currentQuestion.answers
        let totalProgress = Float(questionIndex) / Float(questions.count)

        navigationItem.title = "Question #\(questionIndex+1)"
        questionLabel.text = currentQuestion.text
        questionProgressView.setProgress(totalProgress, animated: true)

        switch currentQuestion.type
        {
            case .single:
                updateSingleStack(using: currentAnswers)
            case .multiple:
                updateMultipleStack(using: currentAnswers)
            case .ranged:
                updateRangedStack(using: currentAnswers)
        }

    }

    func updateSingleStack(using answers: [Answer])
    {
        singleStackView.isHidden = false
        singleButton1.setTitle(answers[0].text, for: .normal)
        singleButton2.setTitle(answers[1].text, for: .normal)
        singleButton3.setTitle(answers[2].text, for: .normal)
        singleButton4.setTitle(answers[3].text, for: .normal)
    }

    func updateMultipleStack(using answers: [Answer])
    {
        multipleStackView.isHidden = false
        multiLabel1.text = answers[0].text
        multiLabel2.text = answers[1].text
        multiLabel3.text = answers[2].text
        multiLabel4.text = answers[3].text
    }

    func updateRangedStack(using answers: [Answer])
    {

    }

}